High-frequency generator



Filed July 22. 1947 May 22, 1951 INVENTOR.v ANGELO MONTANI r ATTORNEY Patented May 22, 1 951 UNITED STATES PATENT OFFICE HIGH-FREQUENCY GENERATOR Angelo Montani, Woodhaven, N. Y., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application July 22, 1947, Serial No. 762,663

Claims. I

The present invention relates in general to space discharge devices and particularly to space discharge devices of the electron beam type.

It has heretofore been proposed to velocity modulate a beam of electrons, by various means, thus causing the electrons in said beam to group themselves into bunches and to cause these bunches of electrons to energize a resonant circuit.

It is an object of the present invention to provide an improved space discharge device of the electron beam type for producing high frequency oscillations.

Another object of the invention is the provision of new and improved means for velocity modulating a beam of electrons.

Still another object of the invention is to provide an improved generator capable of producing high frequency currents under the control of a relatively low frequency.

A feature of the invention is the provision of a space discharge device which may be used as a frequency multiplier.

Briefly these objects and features are accomplished by providing a tube similar in structure to a conventional cathode ray tube but having a plurality of grid segments spaced along the path traced by the electron beam each successive grid segment being charged with a potential of opposite polarity. A resonant circuit is connected to a pair of energy extracting grids which are positioned so as to intercept the groups of bunched electrons. A collecting anode is positioned at one end of the tube and the other end of the tube is provided with conventional electron gun, beam forming electrodes, and beam rotating electrodes. The beam of electrons is rotated across the velocity controlling grids thereby causing the electrons to bunch together at a certain distance beyond said grids at which time they pass through the energy extracting grids and are subsequently collected and returned to the cathode circuit.

The invention will be better understood from the following description when considered in conjunction with the accompanying drawing. Referring to the figure, there is shown a cathode ray tube having the conventional heater l, cathode 2, and beam forming electrodes 3, 4, and 5, all of which are energized by a suitable battery l3, or the like. The pencil-like electron beam, indicated by the broken line l9, passes between a pair of horizontal deflecting electrodes 6 and vertical deflecting electrodes 1. By applying a voltage from the control oscillator I5, to the horizontal deflecting electrodes 6, and to the vertical deflecting electrodes I through a ninety degree phase shifter It, the electron beam is caused to rotate, passing through grids 9, I0, and II, and describing a closed circular path on the collecting electrode l2. It is to be understood that the equivalent magnetic deflecting coils or other suitable means may be substituted for the electrostatic deflecting electrodes, if desired.

The velocity of the electrons is nearly constant as they approach the velocity controlling grid 9. This grid is made up of an even number of separate grid segments arranged in a circle as is shown, each segment being separated from adjacent segments. Each grid segment is charged with an equal potential from battery i l, or the like, but each segment has a polarity opposite to the polarity of the adjacent segments. Thus as the electron beam is circularly swept across successive grid segments it encounters successive electrostatic fields of equal strength but of opposite directions. The velocity of the electrons as they approach the velocity controlling grid 9 is essentially constant and is determined by the potentials on electrodes 3, 4, 5, and 12. As the electrons come under the influence of grid 9 they will either be accelerated or retarded depending upon the polarity of the particular grid segment which they are approaching. It is apparent, then, that the grid segments having a negative charge will produce an electrostatic field such that the electrons passing therethrough will be retarded and conversely, the grid segments having a positive charge will produce an electrostatic field such that the electrons passing therethrough will be accelerated. Thus as the electron beam sweeps across successive grid segments, the electrons emerging from grid 9 have new velocities resulting in a bunching of the electrons at a certain distance from the grid 9. This distance, of course, depends upon the initial velocity of the electrons as they approach grid 9 and the potential on the grid segments of grid 9 which in turn determines the strength of the electrostatic field produced by each grid segment. The number of bunches or groups of electrons which form during a particular unit of time depends upon the number of grid segments comprising grid 9 and the speed of rotation of the electron beam or in other words, the number of grid segments encountered. by the electron beam per unit of time.

It is thought unnecessary to give a detailed explanation of the electrostatic fields appearing around grid 9 and the theory explaining the bunching of the electrons, the theory of velocity modulation being well known in the art.

The energy extracting grids l and I l are placed in such a position as to intercept the electrons just as they have grouped into bunches. If the frequency with which bunches of electrons pass through grids l0 and H is compatible with the natural period of oscillation of the resonant circuit composed of elements I! and I8, then this circuit will oscillate at its resonant frequency. It is understood that the resonant circuit absorbs energy only when a retarding electrostatic field exists across grids I0 and Il. After passing through grid II, the electrons impinge upon the collecting electrode [2 and are returned to the cathode circuit in an obvious manner.

While I have shown an external resonant circuit connected to grids l0 and II, it is to be understood that my invention is not limited to such a resonant circuit. Grids l0 and H and circuit elements I1 and I8 may be replaced by a cavity resonator of any suitable type such as, for instance, the cavity resonator used in the well known Klystron tube.

From the foregoing description it is seen that my invention provides a high frequency generator of the velocity modulated type which may be made to oscillate over a Wide range of frequencies without the necessity of complicated adjustments. For a given number of grid segments in grid 9, my invention may be made to oscillate at many different frequencies simply by tuning the resonant circuit and by changing the frequency of the control oscillator which, of course, adjusts the speed of rotation of the electron beam. Furthermore it is apparent that my invention may be used as a frequency multiplier since the frequency of the oscillations produced is a function of the frequency of the control oscillator.

While what is now considered to be the preferred form of the invention has been illustrated, it is to be understood that numerous modifications may be incorporated therein without departing from the true spirit and scope of the invention as defined in the subjoined claims.

What is claimed is:

1. A space discharge device comprising a source of electrons, means for deriving a beam of electrons from saidsource, means for causing said beam to rotate through a desired repetitious path, a velocity controlling electrode in said path, means associated with said electrode for causing the velocity of the electrons of said beam to alternately and periodically decrease and increase to thereby velocity modulate said rotating electron beam.

2. A space discharge device comprising a source of electrons, means for deriving a beam of electrons from said source, a velocity controlling grid comprised of a plurality of separate grid segments, means for causing said beam to pass through successive grid segments, means associated with said segments for causing the velocity of the electrons of said beam to alternately and periodically decrease and increase to thereby cause said beam to be velocity modulated.

3. A space discharge device comprising a source of electrons, means for deriving a beam of electrons from said source, a velocity controlling grid comprised of an even number of grid segments each insulated from each adjacent segment, means for oppositely polarizing adjacent grid segments, means for causing said beam to pass successively through each grid segment to thereby cause said electron beam to be velocity modulated.

4. An electron discharge device comprising a source of electrons, means for deriving a beam of electrons from said source, a velocity controlling grid comprised of an even number of oppositely polarized grid segments, an extractor circuit resonant to a particular frequency, means for causing said beam to successively pass through each of said grid segments to thereby cause said beam to be velocity modulated, said velocity modulated beam causing said extractor circuit to oscillate at said particular frequency.

5. An electron discharge device comprising a source of electrons, means for deriving a beam of electrons from said source, a velocity controlling grid comprised of an even number of oppositely polarized grid segments, a pair of extracting grids at all times in intercepting relation with said beam, a circuit resonant at a particular frequency associated with said extracting grids, means for causing said beam to suecessively pass through each of said grid segments to thereby cause said beam to be velocity modulated, the passage of said modulated beam through said extracting grids causing said resonant circuit to oscillate at said particular frequency.

6. An electron discharge device comprising a source of electrons, means for deriving a beam of electrons from said source, a velocity controlling grid comprised of a number of oppositely polarized grid segments, a pair of extracting grids at all times in intercepting relation with said beam, a circuit associated with said extracting grids, means including an alternating voltage of a particular frequency for causing said beam to successivel pass through each of said grid segments to thereby cause said beam to be velocity modulated, the passage of said beam through said extracting grids causing said circuit to oscillate at a frequency equal to multiple of said particular frequency.

7. In a cathode ray tube having heater, cathode, and focusing electrodes of the electron gun type for producing a beam of electrons, and having beam deflecting electrodes for causing said beam to scan a desired repetitious path, a velocity controlling grid comprised of a plurality of oppositely polarized grid segments located in said path for velocity modulating said beam of electrons, a pair of extracting grids located in said path, a resonant circuit associated with said extracting grids, the passage of said beam through said extracting grids causing said circuit to oscillate.

8. In a frequency multiplier, a cathode ray tube in which an electron beam is caused to repeatedly scan a certain path on a collecting plate, a pair of grids interposed in said path and successively intercepting said beam, a series of grids also successively interposed in the path of said beam, bunching means associated with said grids of the series to cause said grids of the series to velocity modulate the electrons in said beam, whereb said electrons are caused to pass said first pair of gridsin bunches, and an oscillating circuit connected to said pair of grids and caused to oscillate by the passage of said bunched electrons through said first pair of grids.

9. The method of modulating the velocity of the electrons in an electron beam which consists in causing the beam to repeatedly traverse a certain path and to successively traverse a se ries of oppositely poled grids interposed in said path whereby said electrons are bunched at a certain distance beyond said series of grids.

10. The method of modulating the velocity of the electrons in an electron beam to thereby 5 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,086,904 Evans July 13, 1937 2,250,528v Gray Jul 29, 1941 2,405,519 Rajchman Aug. 6, 1946 FOREIGN PATENTS Number Country Date 468,185 Great Britain June 30, 1937 

